I just started working on a patch to add #if guards, and the first interesting
thing I found was the basic_string constructor:
> template <class _CharT, class _Traits, class _Allocator>
> template <class _Tp>
> basic_string<_CharT, _Traits, _Allocator>::basic_string(
> const _Tp& __t, size_type __pos, size_type __n, const
> allocator_type& __a,
> typename
> enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
> void>::type *)
> : __r_(__second_tag(), __a)
> {
> __self_view __sv = __self_view(__t).substr(__pos, __n);
> __init(__sv.data(), __sv.size());
> #if _LIBCPP_DEBUG_LEVEL >= 2
> __get_db()->__insert_c(this);
> #endif
> }
I suppose the decision was made so that std::string could take advantage of it.
Is it a conforming extension?
> On Jun 15, 2017, at 18:35, Eric Fiselier <e...@efcs.ca> wrote:
>
> It *shouldn't* include <string_view>, that's a given.
>
> IIRC, and Marshall would know better, I believe it was untenable to
> maintain a version of <string> that didn't depend on <string_view> after
> making
> the changes required for C++17.
>
> However inspecting <string> now it does seem possible that the entanglement
> is avoidable.Though it's also likely I'm just not seeing the whole picture.
>
> /Eric
>
> On Thu, Jun 15, 2017 at 6:42 PM, Duncan P. N. Exon Smith
> <dexonsm...@apple.com <mailto:dexonsm...@apple.com>> wrote:
>
> > On Jul 20, 2016, at 22:31, Marshall Clow via cfe-commits
> > <cfe-commits@lists.llvm.org <mailto:cfe-commits@lists.llvm.org>> wrote:
> >
> > Modified: libcxx/trunk/include/string
> > URL:
> > http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/string?rev=276238&r1=276237&r2=276238&view=diff
> >
> > <http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/string?rev=276238&r1=276237&r2=276238&view=diff>
> > ==============================================================================
> >
> > @@ -435,6 +461,7 @@ basic_string<char32_t> operator "" s( co
> > */
> >
> > #include <__config>
> > +#include <string_view>
>
> This breaks the following, valid, C++14 code:
>
> #include <string>
> #include <experimental/string_view>
> using namespace std;
> using std::experimental::string_view;
> void f() { string_view sv; }
>
> Should <string> #include <string_view> even when we're not in C++17 mode?
> Why?
>
> > #include <iosfwd>
> > #include <cstring>
> > #include <cstdio> // For EOF.
>
>
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